The electrical properties of excitable cells are determined in large part by the voltage-gated K.sup.+ channels, i.e., "Kv channels", present on the plasma membrane of such cells. Kv channels are also important in many nonexcitable cells where they contribute to diverse processes such as volume regulation, hormone secretion, and activation by mitogens. At least 50 different Kv channel genes have been identified, and most have been assigned to one of the following four major subfamilies: Kv1, Kv2, Kv3, and Kv4. Each Kv channel gene encodes a single pore-forming subunit, referred to as the .alpha.-subunit. Functional Kv channels are formed by the tetrameric association of individual .alpha.-subunits. With multiple Kv.alpha. proteins that assemble as multi-subunit heteromeric complexes, there may be hundreds of functionally distinct Kv channels.
Kv channels, either functioning or malfunctioning, are implicated in many disease states including cardiac arrhythmias, hypertension, angina, asthma, diabetes, renal insufficiency, urinary incontinence, irritable colon, epilepsy, cerebrovascular ischemia and autoimmune diseases Accordingly, efforts are underway to identify and characterize pharmacological agents that alter the kinetics, gating or formation of Kv channels. The efficacy of such agents is determined by treating cells with such agents and measuring changes in current across the plasma membrane of the cells. Unfortunately, it is difficult to measure small changes in the current in most cells. It is also difficult to determine whether a pharmocological agent alters current flow through a specific Kv channel. Accordingly, it is desirable to have methods and tools which can be used to regulate the numbers and types of Kv channels on the plasma membrane of cells. It is also desirable to have new research tools that can be used for examining the assembly and synthesis of Kv channels.